.\" -*- nroff -*-
.\" Copyright 2010 Cisco Systems, Inc.  All rights reserved.
.\" Copyright 2006-2008 Sun Microsystems, Inc.
.\" Copyright (c) 1996 Thinking Machines Corporation
.\" $COPYRIGHT$
.TH MPI_Is_thread_main 3 "Jun 10, 2020" "4.0.4" "Open MPI"

.SH NAME
\fBMPI_Is_thread_main\fP \- Determines if thread called MPI_Init

.SH SYNTAX
.ft R
.SH C Syntax
.nf
#include <mpi.h>
int MPI_Is_thread_main(int *\fIflag\fP)

.fi
.SH OUTPUT PARAMETERS
.TP 1i
flag
True if calling thread is main thread (boolean).
.ft R
.TP 1i
IERROR
Fortran only: Error status (integer).

.SH DESCRIPTION
.ft R
MPI_Is_thread_main is called by a thread to find out whether the
caller is the main thread (that is, the thread that called MPI_Init or
MPI_Init_thread).

.SH ERRORS
.ft R
Almost all MPI routines return an error value; C routines as
the value of the function and Fortran routines in the last argument. C++
functions do not return errors. If the default error handler is set to
MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism
will be used to throw an MPI::Exception object.
.sp
Before the error value is returned, the current MPI error handler is
called. By default, this error handler aborts the MPI job, except for
I/O function errors. The error handler may be changed with
MPI_Comm_set_errhandler; the predefined error handler MPI_ERRORS_RETURN
may be used to cause error values to be returned. Note that MPI does not
guarantee that an MPI program can continue past an error.
.sp
See the MPI man page for a full list of MPI error codes.

.SH SEE ALSO
.ft R
.nf
MPI_Init
MPI_Init_thread

